Technical Field
The disclosure herein relates to a fairing installed in a bypass duct and particularly to a fairing installed in a bypass duct for rectifying a bypass flow in a low bypass ratio turbofan engine and a turbofan engine therewith.
Description of the Related Art
In a turbojet engine, hot gas flow generated by a combustor, if ejected aftward with no change, has excessive velocity relative to the flight speed, and therefore generates great resistance to the ambient air. This leads to little expectation of high thrust efficiency particularly in low flight speeds. This problem may be solved by conducting part of air flow generated by a fan or a compressor thereof to bypass a core engine into a bypass duct and then ejecting it aftward. An engine of this type is referred to as a turbofan engine, which is well known because the bypass flow having proper velocity relative to the ambient air prominently improves thrust efficiency.
The ratio of the amount of air flowing into the bypass duct to the amount of air flowing into the core engine is referred to as a bypass ratio. In engines used for aviation up to subsonic speeds, bypass ratios of four or more, namely high bypass ratios, are selected. Because it is expected to improve fuel efficiency as the bypass ratio is increased, engines with bypass ratios that exceeds eight are recently in practical use. In order to minimize energy loss, in a normally selected structure, a bypass duct is shortened to eject the bypass flow directly into the ambient air.
On the other hand in a case where supersonic aviation is attached weight, as it requires high velocity flow, low bypass ratio turbofan engines with bypass ratios of two or less are used. In contrast to those with high bypass ratios, bypass flow is conducted through a relatively long bypass duct to a part just behind a turbine and is mixed there and ejected through a nozzle. More specifically, in general, low bypass ratio turbofan engines have inherent structural differences as compared with those with high bypass ratios apart from a difference in the bypass ratios.
The following documents disclose related arts.                Japanese Unexamined Patent Application Publication No. S54-27613        Japanese Unexamined Patent Application Publication No. 2005-113919        